A diesel particulate filter (DPF) is used to remove soot from diesel exhaust. The exhaust passes through the DPF and soot is captured with an efficiency of up to 99%. Over time the soot accumulates in the filter and must be eliminated to avoid development of a large back pressure in the exhaust system. Soot removal occurs through what is termed regeneration of the filter.
One novel approach uses a potassium containing glass as a catalyst, in which K+ ions are present within a silicate matrix. For instance, in U.S. Pat. No. 8,356,475, incorporated herein by reference in its entirety, discloses the use of DPF having potassium containing glasses as catalysts for soot oxidation. This approach relies on the slow passive release of potassium from a silicate glass network to provide for renewal of the catalytic surface activity of the glass. With exposure to water vapor, ion exchange of H+ and potassium ions can occur, promoting migration of K+ to the glass catalyst surface and providing a continuous supply of potassium for long term catalytic soot combustion. This mitigates the effect of loss of the active potassium species during combustion by providing new ions over time. In at least one trial, for the glass compositions disclosed in the earlier issued patent, soot combustion temperatures in the range of approximately 375-400° C. were achieved.
While the previous DPF and catalysts are sufficient for its intended purposes, there remains an identifiable need for various additional DPF and catalyst combinations for differing operating conditions.